WASH and the Arp2/3 complex regulate endosome shape and trafficking

Abstract

Activators of the Arp2/3 complex, termed nucleation-promoting factors (NPFs), are required for the proper spatial and temporal control of actin assembly in cells. Mammalian cells express several NPFs, each of which functions in a distinct cellular process, including WASP and N-WASP in phagocytosis and endocytosis, WAVE and JMY in cell migration, and WHAMM in ER-to-Golgi transport. Although another NPF called WASH was recently identified, the cellular localization and function of this protein were unclear. Here we demonstrated that human WASH alone potently activated the Arp2/3 complex in vitro and in cells, suggesting that the protein is not autoinhibited like N-WASP, but is likely regulated by interacting proteins. In cells, WASH was associated with Rab5-positive early endosomes and Rab11-positive recycling endosomes that were enriched for actin filaments. Silencing of WASH or Arp2/3 complex expression by RNAi, or disruption of actin function by drug treatments, caused enlargement and elongation of endosomes. Intriguingly, WASH silencing, as well as actin disruption, delayed EGF transport to LAMP1-positive late endosomes. These observations indicate that actin polymerization by WASH influences the shape and maturation of endosomes, and highlight a previously unrecognized role for WASH and the Arp2/3 complex in the degradative steps of endocytic trafficking. V C 2010 Wiley-Liss, Inc.

Missense variant in CCDC22 causes X-linked recessive intellectual disability with features of Ritscher-Schinzel/3C syndrome

“…The WASH complex controls the polymerization of actin at the surface of endosomes through the activation of the Arp2/3 complex, a major actin nucleator. 17 WASHdependent actin polymerization promotes scission of transport intermediates of the different endosomal routes and affects recycling, 17 degradation, 18 and retrograde pathways. 19,20 Inactivating variants in the gene encoding the WASH subunit strumpellin has been recently shown to cause a form of RSS/3C syndrome.…”

Cellular functions of WASP family proteins at a glance

“…WASH localizes to endosomes (Derivery et al, 2009;Gomez and Billadeau, 2009;Harbour et al, 2012;Jia et al, 2012;Monfregola et al, 2010;Monteiro et al, 2013;Ryder et al, 2013), and WASHgenerated F-actin not only regulates the architecture of the endolysosomal system, but also spares specific cargo from lysosomal degradation or missorting (Bartuzi et al, 2016;Derivery et al, 2009Derivery et al, , 2012Duleh and Welch, 2010;Gomez and Billadeau, 2009;Gomez et al, 2012;Monteiro et al, 2013;Zech et al, 2011). WASH is recruited to retromer-positive endosomal subdomains via the interaction of the extended C-terminal tail of FAM21 with the retromer subunit VPS35 (Harbour et al, 2012;Jia et al, 2012).…”

WASH drives early recycling from macropinosomes and phagosomes to maintain surface phagocytic receptors

“…and β2-adrenoreceptor as well as in targeting the epidermal growth factor receptor (EGFR) to the lysosome (23,25,28,29,31). The WASH complex also directly interacts with the retromer sorting complex and is thus required for the specific retrieval of retromer cargos from several endocytic compartments (23,32).…”

“…In particular, significant progress has been made in defining the role of actin in the segregation and extraction of specific proteins (22). Many studies describe a role for the WASH (WASP and SCAR homolog) complex in driving endosomal actin polymerization (23)(24)(25)(26)(27)(28)(29)(30). WASH has been implicated in the endosome-to-surface trafficking of a number of cargos, including the transferrin receptor (TfnR), α5β1 integrins,…”